1. Field of the Invention
The present invention relates to a bicycle frame and more particularly, to a foldable bicycle frame that can conveniently be carried by the user when it is set in the folded non-operative position.
2. Description of the Related Art
FIG. 13 shows a foldable bicycle frame according to the prior art. According to this design, the foldable bicycle frame 70 comprises a top tube 71, a folding structure 80 coupled between the two parts of the top tube 71, a head tube 72 at one end of the top tube 71, a seat tube 73 at the rear end of the top tube 71, seat stays 74 obliquely backwardly extended from the seat tube 73, and chain stays 75 connected to the seat stays 74. Further, the head tube 72 holds a front fork with a handlebar at the top and a front wheel the bottom (not shown). The seat tube 73 supports a seat pillar with a saddle (not shown). Further, a rear wheel (not shown) is pivotally provided at the connection area between the seat stays 74 and the chain stays 75.
The folding structure 80 comprises a base frame 81 and a movable frame 82 respectively affixed to the two parts of the top tube and hinged together, and a quick-release lock 83 adapted to lock the movable frame 82 to the base frame 81. When the quick-release lock 83 is locked, the movable frame 82 is locked to the base frame 81, and the top tube 71 is held in the operative position (see FIG. 13). On the contrary, when unlocked the quick-release lock 83, the movable frame 82 can be turned relative to the base frame 81 to let the foldable bicycle frame 70 be set in the folded non-operative position (see FIG. 14).
The design of foldable bicycle frame 70 can easily be set between the folded non-operative position and the extended operative position. However, when the foldable bicycle frame 70 is folded up, the folded top tube 71 is not locked in the folded position and tends to be vibrated by an external force accidentally. Vibrating the received foldable bicycle frame 70 may cause the folding structure 80 to break. Further, when the foldable bicycle frame 70 is folded up, the two parts of the folded top tube 71 is not kept in parallel, i.e., a big contained angle is defined between the two parts of the folded top tube 71 and the front wheel and rear wheel of the folded bicycle frame 70 are not kept in parallel, resulting in a carrying inconvenience. When the user pulls the folded bicycle frame 70 on the ground, the folded bicycle frame 70 cannot be moved steadily and will fall to the ground. Further, this structure of foldable bicycle frame 70 still occupies much storage space when folded up.